title: Modelling the impact of antibiotic use on antibiotic-resistant Escherichia coli using population-based data from a large hospital and its surrounding community.
abstract: OBJECTIVE
  To determine the temporal relationship between antibiotic use and incidence of antibiotic-resistant Escherichia coli in both the inpatient and outpatient setting of a large urban area.
  
  
  METHODS
  A retrospective observational time-series analysis was performed to evaluate the incidence of non-duplicate clinical isolates of E. coli resistant to ciprofloxacin, trimethoprim/sulfamethoxazole and cefepime from January 2000 through December 2007, combined with a transfer function model of aggregated data on antibiotic use in both settings obtained from the hospital's pharmacy and outpatient billing offices.
  
  
  RESULTS
  Ciprofloxacin resistance increased from 6.0% (2000) to 15.4% (2007; P<0.0001) and cefepime resistance from 0.9% (2002) to 3.2% (2007; P=0.01). Trimethoprim/sulfamethoxazole resistance remained stable (23.7%-25.8%). Total antibiotic use increased in both settings, while fluoroquinolone use increased significantly only among outpatients. A temporal effect between fluoroquinolone resistance in community E. coli isolates and outpatient use of ciprofloxacin (immediate effect and time lag 1 month) and moxifloxacin (time lag 4 months) was observed, explaining 51% of the variance over time. The incidence of cefepime resistance in E. coli was correlated with ciprofloxacin use in the inpatient (lag 1 month) and outpatient (lag 4 months) settings and with the use of ceftriaxone (lag 0 month), piperacillin/tazobactam (3 months) and cefepime (3 months) in the hospital (R2=51%).
  
  
  CONCLUSIONS
  These results support efforts to reduce prescribing of fluoroquinolones for control of resistant E. coli including extended-spectrum β-lactamase producers and show the added value of time-series analysis to better understand the interaction between community and hospital antibiotic prescribing and its spill-over effect on antibiotic resistance.
authors.affiliation: Pharmacy Department, University of Geneva Hospitals and Medical School, Geneva, Switzerland. nathalie.vernaz@hcuge.ch
authors.forename: Nathalie
authors.initials: N
authors.lastname: Vernaz
authors.forename: Benedikt
authors.initials: B
authors.lastname: Huttner
authors.forename: Daniel
authors.initials: D
authors.lastname: Muscionico
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Salomon
authors.forename: Pascal
authors.initials: P
authors.lastname: Bonnabry
authors.forename: José Maria
authors.initials: JM
authors.lastname: López-Lozano
authors.forename: Arielle
authors.initials: A
authors.lastname: Beyaert
authors.forename: Jacques
authors.initials: J
authors.lastname: Schrenzel
authors.forename: Stephan
authors.initials: S
authors.lastname: Harbarth
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D017714:Community-Acquired Infections / Q000188:drug therapy / Q000382:microbiology; D003428:Cross Infection / Q000188:drug therapy / Q000382:microbiology; D024881:Drug Resistance, Bacterial; D004363:Drug Utilization / Q000706:statistics & numerical data*; D004926:Escherichia coli / Q000187:drug effects* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000188:drug therapy* / Q000382:microbiology*; D006761:Hospitals; D006801:Humans; D015233:Models, Statistical; D012189:Retrospective Studies
chemical_list: D000900:Anti-Bacterial Agents